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oe1(光电查) - 科学论文

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出版时间
  • 2018
研究主题
  • Schottky diodes
  • frequency multipliers
  • submillimeter-wave technology
  • terahertz technology.
  • Submillimeter-wave sources
应用领域
  • Optoelectronic Information Science and Engineering
机构单位
  • California Institute of Technology
201 条数据
?? 中文（中国） ▾

  • Fast Modeling Methods for Estimating Imaging Performance of Whole Body Screening

    摘要： Simulation of millimeter wave imaging system for whole body screening before a safety inspection manufactured is a challenging work. The conventional physical optics (PO) method is a proper high-frequency approximation method to solve the forward problem of imaging. In this letter, a modi?ed PO method is used to calculate not only metal scatterer but also non-metal dielectric medium. A ray tracing (RT) method and its modi?cation are proposed to further fast estimate the performance of multiple-input-multiple-output (MIMO) imaging system. The radiation pattern of transmitter or receiver is taken into account, then the rough imaging performance of arbitrary MIMO system on arbitrary human posture can be acquired in seconds to make the system design ?exible and convenient. The image reconstruction of the proposed method for a human body model with dielectric skin medium and metal pistol has demonstrated the applicability to real-life applications.

    关键词： Millimeter wave imaging,concealed weapon detection (CWD),Image reconstruction,Physical optics (PO),Ray tracing (RT),Multiple-input-multiple-output (MIMO)

    更新于2025-09-10 09:29:36

  • Design and Experimental Evaluation of Equalization Algorithms for Line-of-Sight Spatial Multiplexing at 60 GHz

    摘要： With large bandwidths, millimeter wave (mmWave) line-of-sight (LoS) MIMO technology employing parallel stream transmission is well suited for future wireless backhaul systems. However, hardware imperfections of mmWave transceivers cause additional signal processing challenges. Considering the channel and hardware properties, this work proposes a novel frame structure with high temporal efficiency. The required MIMO processing can be decomposed into two steps. The first one removes the interantenna interference including the carrier frequency offsets. In the second step, the intersymbol interference brought by the frequency-selective components is cancelled with a parallel structure. As a comparison, a more general decision-directed least mean square approach (DD-LMS) for joint processing of all effects is introduced. With a 60 GHz 2×2 LoS MIMO demonstrator, only the widely linear version of DD-LMS achieves performance of about 0.2dB~0.6dB better than the proposed method, but requires approximately 4 times more complexity. The proposed method with parallel processing chains is well suited especially for larger LoS MIMO systems, e.g., for a system with 16 streams, its required complexity is less than 7% of the widely linear DD-LMS.

    关键词： Channel Equalization,MIMO,Line of Sight,Synchronization,Backhaul,Millimeter Wave

    更新于2025-09-10 09:29:36

  • Generation of rogue waves in gyrotrons with high excess over the threshold

    摘要： Many physical systems exhibit behavior associated with the emergence of the so-called rogue waves which represent dramatically high-amplitude events that occur with low probability but much more frequently than expected in ordinary wave statistics [1]. For example, in laser physics and optics rogue waves arise in the process of supercontinuum generation and represent pulses of ultra broadband light with extremely high peak power [2]. In this paper within the framework of the average approach and in direct 3D PIC (particle-in-cell) simulations we demonstrate that rogue waves can also appear in gyrotrons operating with high excess over the threshold. The mechanism of extreme spikes formation is related to simultaneous cyclotron interaction of a gyrating electron beam with forward and backward waves near the waveguide cutoff frequency as well as with the longitudinal deceleration of electrons. From the practical point of view, experimental observation of the rogue waves generation in gyrotrons can be interesting as a method for production of high-power millimeter-wave radiation with an ultra broadband spectrum. The required exceeding over the threshold can be achieved for routine parameters of the driving electron beams formed by the magnetron-injection guns due to operation at the lowest modes of microwave cavities.

    关键词： high-power millimeter-wave radiation,rogue waves,gyrotrons,ultra broadband spectrum

    更新于2025-09-10 09:29:36

  • Millimeter wave absorbing property of flexible graphene/acrylonitrile-butadiene rubber composite in 5G frequency band

    摘要： The coming fifth generation mobile communication technology (5G) puts forward enormous requirements on millimeter wave (MMW) absorbing materials above 24 GHz. In the present work, elastic absorbing composites were fabricated with reduced graphene oxide (RGO) of different reduction time and nitrile rubber (NBR). A series of characterization methods were used to study the reduction degree and the structure of composites, the electromagnetic parameters of composites in 26.5–40 GHz were also measured and used to conduct an analytical computation of reflection loss (RL). It was found that, 3h-RGO/NBR presented the minimum RL of ?45 dB at 35.4 GHz while 7h-RGO/NBR exhibited the widest effective bandwidth (<-10 dB) about 6.5 GHz. In addition, the mechanical properties of composites were also improved by RGO. Therefore, the obtained RGO/NBR composites displayed promising prospect as elastic MMW absorbing materials for 5G applications.

    关键词： 5G Frequency Band,reduced graphene oxide,Nitrile rubber,millimeter wave absorbing

    更新于2025-09-10 09:29:36

  • [IEEE 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Espoo, Finland (2018.8.27-2018.9.1)] 2018 12th International Congress on Artificial Materials for Novel Wave Phenomena (Metamaterials) - Self-complementary tessellations as universal design approach for LP-to-CP transforming frequency selective surfaces

    摘要： Recently self-complementary frequency-selective surfaces (FSSs) have been shown capable of linear-to-circular polarization transformation. In this work we numerically and experimentally prove generality of this approach showing that similar self-complementary tessellations can be used as FSS patterns in both the microwave and the sub-millimeter wave ranges. Moreover, we simulated two Escher’s tessellations as patterns of microwave FSSs to further demonstrate the polarization transform function of arbitrary self-complementary FSSs.

    关键词： linear-to-circular polarization transformation,self-complementary tessellations,microwave,sub-millimeter wave,frequency-selective surfaces

    更新于2025-09-10 09:29:36

  • High-Gain Electrically Large Air-Cavity-Backed Patch Antenna Element and Array

    摘要： In this work, single high-gain patch antenna element with electrical large property (ELP) based on TM30 mode is presented. Stable field distribution of the TM30-mode is maintained by using one TE20-mode substrate integrated waveguide (SIW) slot-coupling feed structure. Furthermore, air-cavity-backed structure and metal pins are introduced to expand the antenna bandwidth. The ELP element resonates at 22GHz with simulated -10dB impedance bandwidth of 6.9% and maximum gain of 14.2 dBi. Then in order to correct the asymmetrical field distribution in TE20-mode SIW, differential feed technology is introduced in array design. The feeding network consists of two TE10-TE20 mode planar transducers and one anti-phase power divider. The working principle and design procedure of the ELP array are given in detail accordingly. Finally, a 2×2 ELP array is optimized and fabricated for verification. The measured results show that the array antenna has -10dB impedance bandwidth of 9% and maximum gain of 18.9 dBi. Furthermore, it owns merit of excellent radiation performance with high aperture efficiency of about 90%.

    关键词： high-gain,Array antenna,high-order mode,millimeter-wave,high-aperture efficiency,mode-transducer,electrically large property (ELP),differential feeding network

    更新于2025-09-10 09:29:36

  • [IEEE 2018 15th European Radar Conference (EuRAD) - Madrid, Spain (2018.9.26-2018.9.28)] 2018 15th European Radar Conference (EuRAD) - Differential Multi-Layer Compact Grid Antenna Array for 79 GHz Automotive Radar Applications

    摘要： A novel wide band compact grid antenna array is developed for 79 GHz MIMO radar applications. The key issue is the stable radiation pattern with flat gain characteristic along the whole frequency bandwidth, which is very advantageous for the targeted radar applications. The antenna is taped out with the new high resolution multi-layer PCB technology, called “Any-Layer PCB”. This technology provides the possibility to stack micro-vias in PCB boards and reduce the fabrication cost compared to other multi-layer technologies in mm-wave bands. With this feature, the width of the array has been compacted with 17.2%, which leads to a higher side lobe suppression and an enhancement of the field of view in radar applications. A combined impedance and 3-dB gain band width of 9.6% is achieved. The gain and SLL are 13.52 dB and -14 dB at 79 GHz, respectively.

    关键词： radar applications,multi-layer PCB technology,79 GHz radar,grid antenna array,millimeter wave

    更新于2025-09-10 09:29:36

  • High-Periphery GaN HEMT Modeling up to 65 GHz and 200°C

    摘要： In this article, we report on the temperature-dependent GaN HEMT behavior. To evaluate the potentialities of this kind of active solid-state electronic device at its best, the experiments are performed at extreme operating conditions. As a case study, we consider a large 0.25-μm GaN HEMT with a gate periphery of 1.5 mm, providing a high dissipated power of 5.1 W. The tested semiconductor device is characterized by measuring scattering parameters at high frequencies up to 65 GHz and at high ambient temperature up to 200°C. To assess the impact of the thermal effects on high-frequency GaN HEMT performance, an equivalent circuit is analytically extracted and then used to determine the main RF figures of merit. The achieved experimental results show evidence that the increase of the temperature causes a significant degradation in device performance.

    关键词： scattering parameter measurements,high-power,GaN HEMT,high-temperature,Active solid-state electronic device,millimeter-wave frequency

    更新于2025-09-10 09:29:36

  • Uplink Channel Estimation and Data Transmission in Millimeter-Wave CRAN with Lens Antenna Arrays

    摘要： Millimeter-wave (mmWave) communication and network densification hold great promise for achieving high-rate communication in next-generation wireless networks. Cloud radio access network (CRAN), in which low-complexity remote radio heads (RRHs) coordinated by a central unit (CU) are deployed to serve users in a distributed manner, is a cost-effective solution to achieve network densification. However, when operating over a large bandwidth in the mmWave frequencies, the digital fronthaul links in a CRAN would be easily saturated by the large amount of sampled and quantized signals to be transferred between RRHs and the CU. To tackle this challenge, we propose in this paper a new architecture for mmWave-based CRAN with advanced lens antenna arrays at the RRHs. Due to the energy focusing property, lens antenna arrays are effective in exploiting the angular sparsity of mmWave channels, and thus help in substantially reducing the fronthaul rate and simplifying the signal processing at the multi-antenna RRHs and the CU, even when the channels are frequency-selective. We consider the uplink transmission in a mmWave CRAN with lens antenna arrays and propose a low-complexity quantization bit allocation scheme for multiple antennas at each RRH to meet the given fronthaul rate constraint. Further, we propose a channel estimation technique that exploits the energy focusing property of the lens array and can be implemented at the CU with low complexity. Finally, we compare the proposed mmWave CRAN using lens antenna arrays with a conventional CRAN using uniform planar arrays at the RRHs, and show that the proposed design achieves significant throughput gains, yet with much lower complexity.

    关键词： lens antenna array,antenna selection,fronthaul constraint,millimeter-wave communication,quantization bit allocation,Cloud radio access network,channel estimation

    更新于2025-09-10 09:29:36

  • Design of a MMIC low-noise amplifier in industrial gallium arsenide technology for E-band 5G transceivers

    摘要： The technology, design procedure and measurements of an E-band (71-86 GHz) high performance gallium arsenide (GaAs) low-noise amplifier (LNA) are presented. The latter provides a gain in excess of 20 dB, an average in-band noise figure (NF) of 2.3 dB, absorbing 60 mW DC bias power. A European space-qualified technology (OMMIC’s GaAs 70 nm process) has been selected to demonstrate the feasibility of employing the proposed LNA for production-ready wireless backhaul point-to-point communication systems. A possible installation scenario has been depicted, in order to verify the maximum distance at which TX and RX antennas can be placed and employing the proposed LNA as first amplifying stage of the receiver chain.

    关键词： LNA,GaAs,E-band,MMIC,millimeter wave circuits

    更新于2025-09-10 09:29:36